I want to replace a ceiling electrical box rated for light fixtures with one that is rated for fan support. Unfortunately, I can't seem to get the existing plastic box out with the usual methods. There are no visible screws inside of the box, and putting a 2x4 in there and whacking it with a hammer didn't dislodge it either. I was able to see that it was held in via two screws directly into a ceiling joist from the side of the box.
I don't want to go into the attic to unscrew the box from the joists, so what options do I have to remove this thing? I saw a suggestion online to use pliers and cut out pieces of the box until it's all out, but I don't want to start doing that then find out I still can't remove the box... and be stuck with no light and no fan.
The ceiling box looks similar to this, but it is not held in by nails, it is screwed in.